The present invention relates generally to a method for electronically adjusting the viewing angle of a liquid crystal display. Liquid crystal displays are known to be used on a variety of different devices to provide a visible image converted from signals, normally electronic signals, provided to the display. The image is created by electronically making a pattern from a visual contrast in brightness and/or color from the display surface. The display surface may be a pixel array. Color may be produced by using a three color triad of red, green, and blue for each pixel. Each pixel, being the smallest controllable element of the display, may be turned on and off by individual electronics control to each pixel. By turning on a particular pattern of pixels within the display, a visible image is formed on the display screen.
In present day liquid crystal display technology, the red, green, and blue dot transistors are sandwiched between two glass panels. The liquid crystal fluid is activated by a voltage which changes the plan of polarization causing the dot transistors to admit light in the colors of red, green or blue or a mixture thereof. Liquid crystal displays are finding an increasing number of applications in today's world.
One example of an application for liquid crystal displays is within electronic flight indicators on aircraft instrument panels. Applicants have recently filed other patent applications related to the use of liquid crystal displays within horizontal situation indicators ("HSI") and, in attitude direction indicators ("ADI"). Prior to the present invention, it was thought that a liquid crystal display used in an electronic flight indicator, or other device for that matter, was fixed in its vertical viewing angle.
The vertical viewing angle is perhaps best explained from the viewer's perspective by imagining a liquid crystal display in a fixed location. A viewer of the display (of a normal viewing angle) seated directly across from the display and with his eyes at the same level as the display, sees the display from a perpendicular (normal) angle of zero degrees. However, when the viewer stands up the viewing angle is dramatically increased up to 90 degrees from normal depending upon how close the viewer is standing to the display and the height level at which the viewer's eyes are in space with respect to the level of the display. Thus it can be imagined that as the viewer's eye level changes it would be advantageous to adjust the viewing angle of the display, otherwise the viewer's view of the display will be lessened the greater the disparity between his eye level and the set viewing angle of the display.
Prior to the present invention it was thought that the viewing angle for a liquid crystal display of either a passive or active variety, was fixed with respect to the device in which it is contained. The present inventors discovered the benefit of being able to adjust the viewing angle of a liquid crystal display within an electronic flight indicator fixed in position on a cockpit instrument panel. Throughout the course of a flight, a pilot or co-pilot will likely have his or her eyes at various spatial levels with respect to a given electronic flight indicator. Therefore, as the pilot's eye level rises or is lowered with respect to the indicator the pilot's view of the display would be adversely affected absent some means for adjusting the viewing angle of the liquid crystal display. The aforementioned problem may also be noted when two pilots of different heights attempt to view a liquid crystal display from a seat on a fixed level or, in an aircraft there may be a different location for a flight indicator display with respect to the location for the same display on a different aircraft, which could be better facilitated if the viewing angle of the display itself was adjustable. Therefore, a need exists to enable a liquid crystal display to have an electronically adjustable viewing angle.